1) An amount due; a debt.
2) A grievance that is harbored and requires satisfaction
3) A group of 20 items.
4) The act of securing an advantage, especially a surprising or significant gain.
5) The act or an instance of buying illicit drugs.
6) A successful robbery.
7) A sexual conquest.

1) "that guy owes me a score."
2) "settle an old score."
4) “He had dropped out of school and gone for that quick dollar, that big score” (Peter Goldman).